An Engine Control Module (ECM) for controlling an operation of a vehicle internal combustion engine and a starter motor for starting an operation of the internal combustion engine operate using power from a battery mounted on the vehicle. When the starter motor cranks the internal combustion engine in a state where the battery is deteriorated, a terminal voltage of the battery drops greatly due to power consumption by the starter motor. When this voltage drop is notable, the ECM shuts down instantaneously and restarts.
In a vehicle in which an idle-stop operation, i.e., ceasing an operation of the internal combustion engine when it is running idle and the vehicle is in a stationary state, is performed on the internal combustion engine, an unexpected restart of the ECM during an engine start-up may result in an engine start-up failure. Even if the internal combustion engine could be restarted on this occasion, it is unlikely that the internal combustion engine could be restarted with stability following a subsequent idle-stop operation.
In this context, JP2009-013953A, issued by the Japan Patent Office in 2009, proposes setting a voltage level that may cause an ECM to restart as a reset level in advance, and preventing idle-stop operation control of an internal combustion engine when a terminal voltage of a battery falls below the reset level.